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REPORT ON ZOOLOGY, MDCCCXLII : 
Polythalamia is also an internal one, which is completely enveloped 
by the shell (Microscop. Journ. 1841, p. 104). 
A very comprehensive work, by Dujardin, on the Infusoria, has ap- 
peared (Histoire Nat. des Zooph. Infusoires, 1841). He separates this 
class into two great divisions. Of these, that of the asymmetrical Infu- 
soria corresponds to the polygastric of Ehrenberg ; whilst the other, 
under the definition of Systolides, comprehends the Rotatoria of Ehren- 
berg, with the Tardigrades, which latter have not hitherto been properly 
accommodated to any class of the invertebrata. Doyere has also at- 
tempted to prove an alliance of the Tardigrades with several Rotatoria, 
viz., — Notommata, Diglena, Distemma, Monocerca, and Mastigocerca 
(Ann. d. Sc. Nat. t. 17, p. 193), the mouths of which particularly remind 
us of the Tardigrades. Doyere, at the same time, draws attention to 
the similarity of their muscular parts, their cuticular covering which does 
not become absorbed, the intestinal canal, and the unproportionably 
large eggs in both groups of animals. He has also repeated his experi- 
ments on the revivification of the Tardigrada, Rotifera, and Anguil- 
lulce (Ann. d. Sc. Nat. 1. 18, p. 5, 1’lnstit. 1842, p. 289, Fror. Neue Notiz. 
Bd. 24, p. 232), and has proved, that these animals can be completely 
dried in pure sand, in the open air, in dry air, and in a vacuum, with- 
out losing the capability of being again revived by moisture. When 
these animals were put into hot water of 50 centigr. they were killed 
outright ; but they retained the power of revival when the water was 
at 45 to 48 centigr. When dried individuals were subjected to a great 
heat, there were found among them some which could be revived by 
moisture, even after they had sustained 120-140-145 degrees. He also 
mentions two new species of Macrohiotus, discovered by Quatrefages 
(Ann. d. Sc. Nat. t. 18, p. 34). Ehrenberg has discovered a new infu- 
sorian belonging to the Rotatoria, at Wismar, in the Baltic, and named 
it Dipodina arctiscon (Fror. Neue Notiz. Bd. 24, p. 184). He defines 
it as approximating the genus Notommata, by a particular construction 
of its tarsal nippers. An infusorian, living in the Vaucheria clavata, 
has been made known by Morren as Rotifer vulgaris (ibid. Bd. 18, p. 101). 
Doyere points out some contradictions of Ehrenberg, which have 
occurred to him in his examination of the organs, regarded as the 
sexual parts of the Rotatoria (Ann. d. Sc. Nat. t. 17, p. 199). In 
several species of Notommata, Synchceta, Diglena, &c., Ehrenberg 
defined two simple pouches as testes. In several species of Hydatina, 
Notommata, Cycloglena, Euchlanis, and Brachionus, these two pouches 
are covered with vibrating branchial appendages, and discharge into a 
contractile organ {yesicula seminalis, Ehrenb.) On the other hand, in 
Notommata myrmeleo, syrinx, and clavulata, in which two simple 
pouches, and one furnished with vibratile branchial appendages, dis- 
charge into a contractile organ, the simple pouches, and not that with 
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